The effects of sleep disturbance on a songbird's vocal performance.

Vocal communication serves several critical functions, such as species recognition, mate attraction and resource defence. However, environmental and physiological factors like urbanization, noise pollution and stress can negatively affect vocal performance, especially in birds. While several studies have demonstrated the effects of various disturbances on bird vocalizations, very few have tested how lack of sleep affects birdsong. To investigate the importance of sleep for adult birds' vocalizations, we analysed the vocal performance of captive common mynahs (Acridotheres tristis) after three sleep disturbance experiments: the entire night, first 6 h of the night or last 6 h of the night of sleep disturbance. Sleep disturbances altered song performance, specifically by reducing song output and complexity, but did not affect call output. Sleep disturbances also affected call spectral parameters. These effects varied according to the degree of disturbance, strongest in a full night of sleep disturbance, followed by the first 6 h of the night and last 6 h of the night, respectively. These results indicate that even short-term sleep disturbance can affect adult birds' vocalizations' frequency and structure. These changes could alter birds' communication, negatively impacting social interactions and the acquisition of resources and mates, potentially affecting fitness.